This invention relates to a lighting apparatus for the computer imaging or optical scanning of a surface, particularly a surface having information contained thereon in either a code or alphanumeric format, and in particular, to a lighting apparatus having a lighting source disposed in a light-shielding canopy.
Computer imaging/optical scanning devices were developed to electronically recreate an image of the surface of an object. The electronic image is created by holding the imaging/scanning device directly over the surface to be imaged/scanned. Typically, appropriate lensing focuses the image on a CCD array. The image on the surface is then converted to an electronic signal. Electronic image information is then stored or transmitted to an appropriate data processing apparatus.
To expedite the processing of routine information, computer imaging/optical scanning devices are used to retrieve data or information printed on or affixed to the surface of an object in code or alphanumeric format. A common example is a bar code label affixed to the surface of a package. The bar code label contains information about the package's origin, destination, order number, and the like. To retrieve the information from the bar code label, a computer imaging/optical scanning device electronically recreates a digitized image of the bar code label and transfers that image to a processing computer. The processing computer then deciphers the desired information from the digitized image. Computer imaging/optical scanning devices can be either machine mounted or hand-held. Portable hand-held devices are especially useful when processing is required at remote locations.
The ability to retrieve data or information from the surface of an object depends largely on the quality of the digital image obtained by the computer imaging/optical scanning device. Glare, shadows, non-uniformity in illumination, and interference by ambient light on the surface during the imaging/scanning process can result in degradation of the digital image. A poor digital image leads to loss of data. Uniform illumination over an area is especially important when reading information on an alphanumeric label or in a two-dimensional encoded format. For example, it may be desired to obtain an electronic image of an address label for transmission to optical character recognition devices.
Known computer imaging/optical scanning devices seek to reduce non-uniformity in illumination by using an internal light source to illuminate the surface under review while blocking or masking out interference from ambient light. Such devices, as represented by the patents discussed below, use point light sources in a variety of wavelengths to illuminate the surface to be imaged/scanned. The patents discussed below also disclose the use of a shroud over the surface to block out external light, or the use of light sensors which detect light only in the wavelength generated by the point light source, thereby masking out ambient light during the imaging/scanning process.
Examples of these various computer imaging/optical scanning devices include U.S. Pat. No. 3,996,476 entitled "Low Noise Photoelectric Detector Apparatus," issued to Lazarra on Dec. 7, 1976; U.S. Pat. No. 4,737,653 entitled "Image Sensor with Auxiliary Light Source," issued to Nakagawa, et al. on Apr. 12, 1988; U.S. Pat. No. 4,488,679 entitled "Code and Reading System, " issued to Bockholt, et al. on Dec. 18, 1984; U.S. Pat. No. 4,818,847 entitled "Apparatus for Optically Reading Printed Information" issued to Hara, et al. on Apr. 4, 1989; and U.S. Pat. No. 5,027,418 entitled "Electro-Optical Inspection Apparatus for Printed-Circuit Boards with Components Mounted Thereon," issued to Ikegaya, et al. on Jun. 25, 1991. These patents all disclose the use of point light sources to illuminate the surface to be imaged or scanned. Only U.S. Pat. No. 4,488,679 discloses the use of an exterior enclosure to block out ambient light.
Point light sources, however, do not provide uniform illumination across a surface. Because of their radiation pattern, point light sources can frequently produce glare and/or shadows on the surface resulting in loss of data during the computer imaging/optical scanning process. Furthermore, only U.S. Pat. No. 4,488,679 discloses the use of an exterior hood to prevent ambient light from interfering with the illumination provided by the point light sources.
Accordingly, it is an object of this invention to provide a computer imaging/optical scanning device that provides uniform illumination of the surface to be imaged or scanned.
Further objects and advantages of the invention will become apparent from the detailed description of a preferred embodiment set forth below.